Expansible chamber devices – Mutually relatively movable cylinder or sleeve – member... – With additional cylinder relatively slidable exteriorly of...
Patent
1988-01-28
1989-08-01
Garrett, Robert E.
Expansible chamber devices
Mutually relatively movable cylinder or sleeve, member...
With additional cylinder relatively slidable exteriorly of...
91159, 91167R, 91173, F01B 720
Patent
active
048524646
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a two-stage telescoping hydraulic cylinder with two pistons, one of which slides back and forth inside the other, with cylindrical gaps between the individual telescoping sections, with a pressure-medium line communicating with the cylinder's pressure space, with another pressure-medium line communicating with the cylindrical gap in the first stage and above its floor, and with constant communication between the cylindrical pressure space and the pressure space in the first stage and constant communication between the first stage and the space inside the second stage. A three-stage telescoping cylinder is known from German AS No. 1 107 383.
Two-stage telescoping hydraulic cylinders are mainly operated today in a fixed sequence, with the first stage being extended first, followed by the second stage, and the second stage being retracted first, followed by the first stage. When, however the control valves are appropriately designed, it is also possible to operate the devices in a different sequence, although it is still impossible to extend or retract the stages in known two-stage telescoping hydraulic cylinders simultaneously. It would, however, be desirable in various situations to be able to operate both stages simultaneously. The two stages can of course be operated simultaneously by means of an area-independent displacement system, although the area of the base of the cylindrical gap in the first stage must then of course be exactly as large as the area of the piston in the second stage. A system of this type, however, is so large that it cannot be employed, at least in the applications conventional for this kind of telescoping cylinder, specifically traveling cranes.
With the aforesaid state of the art as a point of departure, the object of the present invention is to allow the two stages of a two-stage telescoping hydraulic cylinder to be operated simultaneously while keeping its dimensions small enough to allow it to be employed in traveling cranes etc.
This object is attained in accordance with the invention in a two-stage telescoping hydraulic cylinder with two pistons, one of which slides back and forth inside the other, with cylindrical gaps between the individual telescoping sections, with a pressure-medium line communicating with the cylinder's pressure space, with another pressure-medium line communicating with the cylindrical gap in the first stage and above its floor, and with constant communication between the cylindrical pressure space and the pressure space in the first stage and constant communication between the first stage and the space inside the second stage in that the space inside the second stage is demarcated by an end plate on the first stage that, in conjunction with the second piston, creates in the second stage a cylindrical gap consisting of communicating sections, in that the cylindrical gap communicates with another pressure-medium line through a telescoping passage that extends through the floor of the first stage and the floor of the second stage to the end plate in the first stage, and in that the cylindrical gap in the first stage and the space inside the second stage are equal in volume.
Since the cylindrical gap in the first stage and the space inside the second stage are equal in volume, this design encompasses telescoping cylinders with stages of differing lengths.
The telescoping cylinder in accordance with the invention can be operated in any way desired, with
(a) both stages extending simultaneously,
(b) both stages retracting simultaneously,
(c) the first stage extending while the second stage remains retracted,
(d) the first stage retracting while the second stage remains retracted,
(e) the second stage extending while the first stage remains retracted, and
(f) the second stage retracting while the first stage remains retracted, stage remains partly extended or retracted and a transition from operations (a) and (b) to operations (c) and (f) and vice versa can always be undertaken.
The aforesaid operations (a) through (f) will be describe
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Bartmann Gunter
Brackelmann Gerd
Denion Thomas
Fogiel Max
Garrett Robert E.
Montan-Hydraulik GmbH
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